1. Field of the Invention
The present invention generally relates to a vibration damper for a motor vehicle suspension system for damping vibrations between, for example, the wheels of the motor vehicle and the body of the motor vehicle. Such a vibration damper will generally have two fluid chambers separated from one another by a piston unit. In addition, there can be a fluid bypass connecting the two chambers. In this regard, a more specific aspect of the present invention generally relates to a shut-off valve module for this fluid connection. The shut-off valve device has at least one shut-off valve which separates a high-pressure section and a low-pressure section of the fluid connection. By means of a magnet armature and a magnet coil, the shut-off valve can typically have a shutoff body which can be adjusted between a closed and an open position by an external control. The high pressure section of the fluid connection can empty into a central channel, and a first side of the shut-off valve body, which first side can be pressurized by the high pressure section, can be elastically pressed against a shut-off valve seat by means of a compression spring. In addition, the first side of the shut-off valve body can be connected by means of an after-throttle to a second side of the shut-of valve body.
2. Background Information
One such shut-off valve module of the type described above is disclosed, for example, in German Patent No. 41 14 305. In general, for the development of an adjustable vibration damper with a shut-off valve module, the characteristics to be achieved by the vibration damper are specified by the vehicle manufacturer. The components of the conventional portion of the vibration damper, and also of the shut-off valve module, are then designed on the basis of these characteristics. It has been found however, that the vibration damper may generate unacceptable hissing noises.
Even an experienced vibration damper designer can typically be unable to determine in advance whether the hissing noises will occur in the finished vibration damper. Basic tests have shown that the hissing noises are: essentially a function of the flow velocity of the damping medium, but no reproducible relationships have been found between the hissing noises and the individual components of the vibration damper. In constructing a vibration damper, the characteristics of the vibration damper must correspond to the needs of the particular vehicle. For this purpose, the sizes of the individual components can essentially be determined, but there are essentially no available measures for preventing hissing noises.